50 Years of High Output Alternators: What We’ve Learned

The electrical demands of buses, coaches, and other large transit vehicles require a lot of power. These vehicles have unique operations that include much time spent with an idle engine, regular stop-and-go travel, and increasingly complex electronic systems for operator use and passenger amenities. 

To meet these needs, transit vehicles have relied on high-output alternators for the last 50 years. These electrical generators provide the heavy-duty electrical power essential to transit operations and applications. As high-output alternators have developed over this past half-century, KIRKS has been working alongside transit engineers and technicians to solve their vehicle maintenance and repair challenges.

High Output Alternators: Then and Now

Automotive alternators are mounted in the engine compartment and draw power from the revolutions or RPM of a vehicle’s engine. As the engine turns, a drive belt and pulley connect to the alternator’s rotor, causing it to spin inside the alternator. This rotation produces a changing magnetic field, which in turn induces a voltage in the alternator’s stator. Finally, the alternator rectifies the stator voltage and provides the current necessary to support the vehicle’s electrical systems.  

Traditional low-output alternators struggled to provide the current needed for buses or coaches. They could not meet transit vehicles’ demands for electrical power, particularly when the engine was idle and at lower RPMs. So, in the 1970s, Delco Remy developed the original high-output alternator designed for transit and coach vehicles: the Delco Remy 50DN. The 50DN’s high-output solved this problem, putting out 270 amps at 5000 RPM, and the 50DN was in every transit bus throughout the 70s and 80s.

“The 50DN Guys”

During these years, KIRKS, then Kirk’s Automotive, Inc., was remanufacturing hundreds of the 50DN alternators every month. Transit authorities from around the country were shipping alternator cores from New York and Dallas to New Jersey and Los Angeles. We were also providing components for them, either tooling up and manufacturing our own or sourcing components at a reasonable cost.

Increasing demand for power

As transit vehicles and travel infrastructure grew, so did the electrical demands of operating these vehicles. Complex technologies built into new buses and the latest gadgetry of today’s passengers require more – cabin lighting, display screens, charging ports, electric cooling fans, and more. With these new loads, ever higher outputs are required.

Today, Delco Remy, C.E. Niehoff & Co., and EMP, among other companies, are producing a variety of high-output alternators ready for today’s transit vehicles. 

  • Delco Remy has modernized and super-charged their original alternator design into the oil-cooled 50DN Plus, outputting 450 amps. While Delco Remy is starting to phase out the 50DN, KIRKS continues to Reman these alternators to service our customers.
  • EMP provides high performance and efficiency, even in extreme conditions. The EMP Power 450, true to its name, outputs 450 amps at 6000 RPM.
  • Niehoff alternators boast a robust, long-lasting design while using less fuel and engine horsepower and exchanging messy oil-cooling for air-cooling. The Niehoff C703 and C706 are 28V, high-efficiency alternators that provide 300 and 350 amps, respectively. The more powerful C803D outputs over 500 amps at 5000 RPM. 

What We’ve Learned: Alternator Failures

Since high-output alternators were introduced in the 1970s, KIRKS has worked with the transit industry and alternator manufacturers to improve the quality and reliable service of heavy-duty alternators. Our years of experience have shown us what maintenance crews deal with when high-output alternators break down and how to help them get what they need for reliable alternator performance.

High-output alternators have a typical life expectancy of about two years. So, a transit bus will see between 5 to 7 alternator replacements across its lifetime. The heavy workload of these components leads to more wear and tear and a short lifespan. Rectifiers, stators, field coils, bearings—any of these or other parts may fail as a natural result of use. In many cases, failure simply results from a component or insulation wearing out. In oil-cooled alternators like the 50DN, heavy use and exposure to heat and vibration cause seals to degrade, leading to oil leaks. 

Learning into Action: Customized Solutions from KIRKS

The engineers at KIRKS take time to learn about the issues customers deal with. They’ve met with engineers, maintenance teams, and technicians to design custom solutions for the weaknesses in high-output alternators. This deep knowledge of alternators, developed over decades of service, has provided KIRKS with the specialized expertise needed to diagnose alternator failures and remanufacture them to meet or exceed OEM specifications. 

Here are a few examples of how our experience has enabled KIRKS to deliver robust and reliable solutions for transit and motor coach markets:

Example: Improperly Replaced Bearings

What bearings should you use in air-cooled alternators like the EMP Power 450?

A local repair shop was repairing heavy-duty alternators with cheaper bearings to save costs, unknowingly causing expensive breakdowns. Bearings keep the rotor spinning smoothly during operation and, thus, are the main wear component inside the alternator. In the original oil-cooled alternators, the flow of oil would lubricate the bearings, but in newer, air-cooled units like the EMP Power 450 or Niehoff C703, the bearings must be sealed with high-temperature shields to hold the original manufacturer’s high-temperature grease. 

Traditional bearings without the proper shields and grease will wear out within months, as the high temperatures of the engine compartment will wear out the shields and allow the grease to escape. Instead, specialized high-temperature grease and shields that can handle up to 1500 C are essential to the longevity of that alternator.

Example: Stop Seal Leaking

How do you stop oil leaks from the Delco Remy 50DN?

When the Delco Remy 50DN was introduced, it was in high demand. Early on, however, maintenance crews were dealing with oil leaking from the front seal. Oil leaks are messy and create new issues. We listened as many transit authorities complained about struggling with this problem. In response, KIRKS engineered a custom solution seal kit for the 50DN that replaces the front seal and addresses this design flaw. 

All KIRKS remanufactured alternators were reassembled with the redesigned seal. Soon, transit authorities that had in-house remanufacturing capabilities were purchasing seal kits in bulk.

Example: Right Fit KitsTM

KIRKS has mobilized its team’s deep technical knowledge to develop our Right Fit Kits.TM
These proprietary kits contain all the components necessary to assemble a remanufactured high-output alternator. Each component included meets OEM specifications and is guaranteed to fit in the assembly.

Transit garages equipped with in-house remanufacturing capability save time and avoid the mess of disassembly, cleaning, and inspection steps in the remanufacturing processes. They move straight to assembly, testing on their KIRKS Transit-Tech 6000 stand and installing their remanufactured alternator into their transit vehicle for reliable performance.

Since 1946, we’re still listening

KIRKS has learned from our close relationships with teams in the transit bus and motorcoach markets. We’ve mobilized our deep technical knowledge to develop solutions. When maintenance crews feel stuck between buying new or choosing unreliable repairs, we find ways to help them escape the parts trap. 

When customers told us what they needed, we listened and innovated solutions. Fifty of our over 75 years in business have included delivering high-output alternator solutions—from our Right Fit Kits, or our Approved EqualTM Remans, to sourcing new or drop-in replacements. We’re still listening and ready to work on new customized solutions. 

From alternators to any of your transit needs, KIRKS is listening to find the perfect fit solution for you. Contact KIRKS today, and let us use what we’ve learned to help you as your partner for parts.